The invention relates to improvements in methods of and in apparatus for condensing vaporous substances. More particularly, the invention relates to improvements in methods of and in apparatus for condensing vaporous substances which are expelled as a result of drying and/or heating of a running web of plastic, textile or other material which carries one or more layers containing one or more volatile substances. Examples of webs which can be treated in accordance with the method of and in the apparatus of the present invention are substrates of paper, fabric, plastic or other materials which carry one or more films of a solvent-containing adhesive.
The application of films to running webs of textile or other material often involves the use of a volatile solvent which is contained in the material of the film or films and must be expelled when the application of the film or films is completed. The solvent cannot or should not be permitted to escape into the surrounding atmosphere. In fact, many countries enforce strict laws which prohibit the release of certain solvents into the atmosphere for ecological reasons. Furthermore, it is often desirable to recover vaporous solvents for renewed use.
Recovery of vaporous substances normally involves heating the running web to promote expulsion of volatile solvent, and thereupon condensing the resulting vaporous substance. The arrangement is or can be such that the normally combustible vaporous substance which is released by a running web into a vapor-collecting chamber is maintained outside of the explosion limits. If the vaporous substance is maintained below the lower explosion limit, the percentage of air is higher which complicates the removal of vaporized solvent. On the other hand, if the vaporized solvent is maintained above the lower explosion limit, the condensing step is relatively simple but expensive precautionary measures must be undertaken in order to prevent contact of vaporous substance with oxygen because this would create the danger of combustion or explosion.